1. Field of Invention
The present invention relates to a method for checking and/or monitoring the leak tightness of a plurality of pneumatically or hydraulically actuated actuators of a machine, in particular a plurality of valve actuators of a medical treatment machine, as well as to a machine, in particular a medical treatment machine, having a control for the carrying out of the corresponding methods.
The present invention in particular relates to a method for checking and/or monitoring the leak tightness of a plurality of pneumatically or hydraulically actuated actuators of a machine in which a cassette system is used for the transport of liquids, in particular medical liquids. The method in accordance with the invention can be used particularly advantageously in the area of dialysis, in particular of peritoneal dialysis, in particular in treatment machines having a cassette system for the transport of the treatment liquids or for the carrying out of the treatment. The method can equally be used in hemodialysis or in infusion systems.
2. Description of the Prior Art
The present invention in particular relates to peritoneal dialysis machines such as are presented in US 2007/0112297 A1 and US 2006/0195064 A as well as to methods for the operation of such peritoneal dialysis machines. The full extent of the content of 2007/0112297 A1 and US 2006/0195064 A1 is hereby an integral part of the disclosure of the present application.
The pneumatically or hydraulically actuable actuators of the machine are advantageously valve actuators with which the valves used in these cassette systems are switched. The cassettes are made as disposable articles and have valve points on which the valve actuators of the machine act and thus switch the valves. The cassettes in particular have liquid conducting passages which have at least one flexible wall in the region of the valve points which can be pressed into the liquid conducting passage by the valve actuator and thus block said passage. In this connection, the actuators advantageously have a flexible region which expands when pressure is exerted on the actuator and thus acts as a valve tappet. Hydraulically or pneumatically actuable pistons can equally be used as actuators which advantageously likewise serve as valve tappets. In such cassette systems, the region advantageously at the cassette side for the conveying of the process liquid such as the dialysate is separated by at least one membrane from the region advantageously at the machine side on which pressure is exerted for the actuation of the actuators.
During ongoing operation of the machine, different switching patterns of the valves are run through to provide the liquid paths required in the cassette e.g. during a purging process or during a treatment. The actuators of the machine have pressured exerted on them for this purpose during the ongoing operation of the machine in different combinations in order thus to switch the corresponding valves in the cassette accordingly and to provide the desired fluid paths for the operation of the cassette.
The actuators usually have an active switching state in which pressure is exerted on them and an inactive switching state in which pressure is not exerted on them. It is possible to switch to and fro between these states by exerting pressure on the actuators or removing the pressure. During such switching processes, the pressure applied to the system changes, whereas a stationary state is adopted between the switchover processes in which the pressure applied to the actuators on which pressure is exerted being substantially constant. However, with pneumatically or hydraulically actuable actuators leaks can occur on the side on which pressure is exerted.
In known methods for checking and/or monitoring the leak tightness of such actuators, an initial test is therefore usually carried out at the start of the treatment in which test pressure is exerted on the actuators and the pressure drop per time unit is measured in the subsequent stationary state to determine any leaks. If the pressure drop per time unit exceeds a certain limit value in this connection, the operation of the device is not released.
A leak present on the initialization of the device can admittedly be recognized with such a method. However, there is no longer any possibility to determine whether a leak has arisen in the system during the operation of the device. In particular no initial test can be carried out during the operation of the machine since the machine would have to be stopped completely for this purpose. Furthermore, there is no indication of when a suitable time for such a test during the treatment would be. Leaks in the actuators can, however, particularly arise during the ongoing treatment due to wear of the actuators.